ZBasic System Library
286
ZBasic Microcontrollers
Type
Subroutine
Invocation
ShiftOut(dataPin, clkPin, bitCnt, val)
Parameter
Method
Type
Description
dataPin
ByVal
Byte
The pin used to output data.
clkPin
ByVal
Byte
The pin used to output a clocking signal.
bitCnt
ByVal
Byte
The number of bits to shift out (1 to 8).
val
ByVal
Byte
The value to shift out.
Discussion
This function can be used to output data to a synchronous serial device like a shift register. The pin
specified for output will be made an output but the pin specified for the clock signal must already be an
output and be at the desired initial logic level.
For each of the number of bits specified, the data pin will be set to the state of the corresponding bit in the
val parameter beginning with the most significant bit first. Then the clock line will be pulsed by changing
its logic level twice.
Data is shifted out MSB first. If a data width of fewer than 8 data bits is specified, the data must be
positioned in the most significant bits of the value and the state of the remaining low order bits in the
value is of no consequence.
Resource Usage
This subroutine uses the I/O Timer. If the I/O Timer is already in use, the subroutine returns immediately.
No other use of this resource should be attempted while the shifting is in progress. Interrupts are
disabled during the shifting process. However, RTC ticks are accumulated during the shifting process so
the RTC should not lose time.
Compatibility
For compatibility with I2C/TWI devices the clock rate is approximately 200kHz with
Register.TimerSpeed1 at its default value of 1. If the value of Register.TimerSpeed1 is changed,
the bit rate will be slower.
See Also
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